Hahaha! That is the worst part, isn’t it? That awkward in-between limbo. Should I? Shouldn’t I? Do I want to risk the friendship? Is it worth the risk if we get together and things don’t work out? The list goes on. sighs and shrugs
To be honest, that’s probably why I prefer dating people I don’t really know that well. You really can’t lose there. If it works out, great. If not, it’s not like you can lose a friendship that was never there. Still, you’re concerns are valid. Sometimes that is the one thing that keeps friendships intact. You both like each other but after dating for a while you both come to decide that you just don’t have the time and it’s better to be friends.
Idk, tho. I tend to think that more results out of fear because I’ve seen people do some amazing stuff to make the time for one another/what/who is important to them. To be honest, though, it doesn’t sound like you are in a hurry and have known the girl for a while. I know the fear always is, “what if someone snatches her up while I wait to move” which does happen from time to time in such situations unfortunately. shrugs For all you know, she’s been thinking about it too and is just waiting for you to actually work up the courage to ask.
That being said, you are going to be a lawyer so down the road there will be plenty of options for you either way if you continue on your path. It doesn’t seem like you are in a rush so I don’t see why you can’t take a casual approach. If you had a good wingman I’d say, spark up a casual conversation with her during a time period were you’d likely both be free for a bit. He approaches while you are in mid-conversation and reminds you that you two were suppose to grab a bit or ask you to come grab something. Something along those lines. shrugs At either rate, you act like you don’t wanna break away from the convo because it’s good… and casually invite her to come along.* She might hesitate. You ask your friend if he minds. He’s like na. Sure. etc etc. You look back at her. If she’s still hesitant you put on a little charm. Maybe a come on. Realistically, even if she wants to come, if she’s the nice type she’s going to play a little coy as if she doesn’t want to impose. You ask a little convincing and boom. Lunch. While walking there you maybe ask him here he wants to go. He doesn’t care and asks you. You either make a decision and look to her to see if that sounds good or shrug it off like you don’t care and ask her what she’s in the mood for. (Can I guess subway? 
)**
Now realistically, the wingman can either stick around for a bit or whatever he wants to do. At some point, though, if the convo is still going well he’ll “have to do something” and bounce leaving the two of you to yourselves.
In that situation some IO might be great. Maybe some IH too. The key is to get a good vibe going and actually learn more about her. If you are good at being subtle and the openings arise, a little harmless flirting/teasing never hurts.
At any rate, at some point you want to excuse yourself. You got to go. You forgot you have something to do. Whatever. You want to leave her wanting more as the saying goes. Maybe a hug good-bye. We’ll have to do this again. etc. etc.
The nice thing about this setting is your pheros should have plenty of opportunity to work in close proximity. IO should assure that you don’t run into awkward pauses or run out of things to talk about. If you go with ammo or something along those lines it should add the addition sexual factor. Etc. etc. I’m sure others could make recommendations as far as the pheros themselves. shrugs
At any rate, it gives you a follow up the next time you catch up. It also opens the door for future lunches because now that she’s gone to lunch with you once and actually enjoyed it there’s something to look forward to as far as doing it again and no need to have an additional person along because she’s already comfortable with doing that with you from the first experience.
This is the slow conquer method. There are variations you can do of this even without a wingman, although a lot of it depends on how convincing you can be. But the key is not to fall into the friendzone. The banter can help. Concerned but a little bit of sexual/flirting/compliments/teasing subtle or otherwise to keep the tension edge. Lunch opens the door to “some friends are going out to the bar/clubs/etc. tonight, you wanna come?” If she got acquainted with your wingman the first time through and she hesitates, you can always be like “come, blah blahs gonna be there too! It’s be fun! Trust me.” or what have you. I’m not saying jump into that immediately. Give the tension a chance to build up. Maybe even vary the levels of attention you give her to keep her guessing.
Regardless, when it all comes down to it, aside from the pheros, be yourself. This doesn’t sound like you are simply going for a pick-up. You want a LTR, yes? So quite frankly, if she doesn’t like you for you than it’s not going to work out anyways. Granted, the pheros give you an additional edge but as long as you are your charming self (which she seems to have warmed to/likes in the first place) I imagine you should be fine.
Granted, this is just a suggestion. Without actually knowing the disposition of the girl and so forth, it’s hard to say with a certainty that approach would work (if you haven’t tried it already). But reading her for clues is always important in this sort of thing and can help you gauge your approach immensely. That’s learned over time, though, so it’s no worries if you aren’t quite sure at this point in time. Just some thoughts. Ok. I’m sorry. I will stop rambling.
*Footnote: Do not leave! She could say she has to go anyways (it’s that not wanting to impose or feel like you just got left kinda a thing, so you pretend to be busy too). That could kill this plan if you can’t talk her into joining. It doesn’t mean there won’t be other opportunities. It just means this approach probably won’t work… at least this time…
In any case, don’t actually leave her like alright, bye. If you can’t convince her, ask him if you can do lunch another time. He’ll be like sure. She might feel bad and tell you to go with your friend. This might open another chance for you to convince her to join from the guilt angle. Or she might give you an excuse why she has to leave. If that’s the case, this might open up the chance to part ways with a verbal commitment for lunch another time then. Maybe even a “you bet” or “sounds good” or “I’ll hold you to that” or something from her (because after she’s given you an excuse she might actually still want to go to lunch but doesn’t want to make it obvious that what she made up was actually an excuse and she isn’t busy).
The final outcome and reason you don’t leave first in this situation is that you staying might make her feel a bit powerful/important. “He blew off his friend for me?” If your conversation continues, and goes well at that, you can move to the “leave her wanting more stage” by pointing out that you are getting hungry and invite her for a bite. If she takes you up on it then you proceed to the one-on-one lunch phase. If she doesn’t then you part with a hug or whatever the case may be and leave her wanting more. Either way, the key again is you being the one that cuts off the interaction first rather than waiting until she’s had enough and “has somewhere to go.” Not only does it have that effect, but when the other person cuts it off you can’t help but wonder if you didn’t do enough. Did they get bored of me? Did I say the wrong thing? Am I less important than a meal? Those kinda subconscious doubts are actually good because they create a bit of a challenge to prove them wrong and add to the chase effect. It’s wierd. Don’t ask me why. They just do.
**Footnote: Depending on the girl… the actual food pick can be a perfect time to tease fun at her and show off your humorous side and/or compliment her. Don’t do it unless it is in your bag of tricks, though. But for example… I might… after you ask her where she would like to go, cut her off before she answers and say, “subway right?” with a coy smile on my face, knowing she’s an athlete. If she response like “how did you guess?”… I can move to turn it into a casual compliment on her physique/athletic prowess and how I’d expect that from an athlete of her calibur. This might actually lead into a conversation about her diet and regmin. This is good and will likely win me brownie points because athletes often like to talk about athletics and such stuff as you have to put a lot of work into your diet and exercise in order to perform at your best (which she likely does).
If she response back with a more like, “What? Why do you say that?” almost playfully or in a light manner (note: tone is important here) I might attack athletes with over-the-top exaggeration. “Don’t you guys all have like nazi diets… blah blah blah…” in a playful way, of course. If I did it right I’ll get a denial in a similar playful manner and I’ll then twist it into a compliment about her physique. It likely could lead into a similar conversation as the first outcome or might remain further light banter. If she becomes more serious in her response to my jab, I’d deflect and emphasize that I was just teasing and go into my compliment as to the reason why I figured that.
In almost any eventuality, I win because it allows me to give her a compliment and make her “feel sexy” or what have you without being overt about it. It will register subconsciously and she might even subtle pick it up and wonder, but it wouldn’t be obvious I’m gunning for her. Finding subtle ways to compliment the other person is an excellent way to charm them. I also find actually subtly picking on them to keep them off balance is also very successful. It’s a process of knocking them down and then flipping it into validation. It kinda masks the compliment and keeps them from thinking they are high up on this “mountain” so to speak. shrugs But that’s just me. I’m no relationship/pick-up advisor/expert. There are just patterns that you pick up on over time but everyone’s got their own style and their own “game” that fits that style the best, so to speak. You just gotta find what works best for you. 
Hehehe… it can be easy to do when ya find a good thing. 